Compiles without warnings!

Foo.hs

{-# LANGUAGE PackageImports #-}
{-# LANGUAGE RankNTypes #-}
module Data.Foo where

import "void" Data.Void as A
import Data.Void as B

foo :: A.Void -> a
foo = absurd

bar :: B.Void -> a
bar x = x ()

test.cabal

name:                test
version:             0.1.0.0
license-file:        LICENSE
author:              Oleg Grenrus
maintainer:          oleg.grenrus@iki.fi
build-type:          Simple
cabal-version:       >=1.10

library
  exposed-modules:     Data.Foo, Data.Void
  ghc-options:         -Wall
  build-depends:       base >=4.7 && <4.8, void == 0.7
  default-language:    Haskell2010

Void.hs

{-# LANGUAGE RankNTypes #-}
module Data.Void where

type Void = forall a b. a -> b